Nick Holonyak developed the first practical LED in 1962. When electrically biased in the forward direction an LED is able to emit light through electroluminescence. The colour of the emission depends on the semi conducting material used, and can be near-ultraviolet, visible or infrared. The semi conducting chip is encased in a solid plastic lens, which is much more resistant than the glass envelope of a traditional light bulb or tube. Most typical LEDs are designed to operate with no more than 30-60 mill watts of electrical power. Around 2000, commercial LEDs capable of continuous use at one watt of input power were introduced. Nowadays 10 watt units will be available with efficiencies of 60 lumens per watt. These devices produce light similar to a 50 watt light bulb, and facilitate the use of LEDs for general illumination needs. The typical working lifetime of an LED is ten years, which is much longer than the lifetimes of most other light sources. Robert N. Hall is usually cited as the inventor of the semiconductor laser, but Holonyak was involved in the development as well. In laser diodes, light is generated basically on the same principle like in LEDs. But by especially designed semiconductor material laser operation is achieved rather than spontaneous luminescence. Within this experiment, properties of LEDs and Laser Diodes like current dependency, spectral and beam characteristics are investigated. The polarization state of the light emitted by the diodes is determined and beam shaping experiments are performed.